1. Field of the Invention
The present invention relates to the field of synchronizing a synchronous signals and finds particular use in synchronizing multiple video type signals in television systems.
2. Description of the Prior Art
The prior art contains many circuits for video synchronizers, beginning with U.S. Pat. No. 4,018,990. These synchronizers generally provide video synchronization by sampling and digitizing the active video portion of a video signal in response to the timing thereof, or in the case of digital video signals recovering the clock and digital samples therefrom, storing the digitized video in a memory. The digitized video is read from the memory at a proper time in response to a reference signal to achieve synchronization thereof. In some devices the digitized video is converted back to a more desirable form, digital or analog or both. Some devices reconstruct and combining the appropriate ones of sync, burst and blanking with the read video.
Video synchronizers for use with single video signals are commonplace in the industry, with multiple video signals being accommodated by use of multiple complete video synchronizers, each being fully self contained. Various techniques and circuits to perform these functions are well known in the art, and emphasis has been placed on improving performance in terms of minimizing noise and distortion from the digitizing process, and improving the immunity of the devices to noise or errors which may be carried with or interfere with the signal which is being synchronized.
The inventive video synchronizer and improvements described herein are designed to allow synchronization of high quality video like signals in analog or digital form (which may include compressed digital form such as MPEG, etc.), while providing minimum distortion and maximum transparency. The invention is particularly well suited for efficiently synchronizing multiple video type signals of mixed or matched form to a desired reference signal. It will be recognized that the inventive teachings herein may be applied equally to analog signals in analog component, composite, serial and parallel and digital data streams in digital serial, parallel, component, composite and compressed form, as well as other forms and standards of electronic signal conveyance.
Because full sync tip to peak white video may be digitized in the analog preferred embodiment shown herein, one would normally expect quantizing errors to be significant. The inventive features of the preferred analog embodiment however show the use of sophisticated digital signal processing techniques-such as oversampling and interpolation, such that these errors are kept to unexpected low levels.
The inventive concepts described herein are applicable for many analog and digital video signal standards, including but not limited to MONOCHROME, SECAM, PAL, NTSC and HDTV versions in analog form, for example the well known RS-330 and RS-170 standards, as well as digital form, for example the well known SMPTE 259 and 260 standards or compressed digital form, for example JPEG, MPEG 1 and MPEG 2. Other functions may be combined with the synchronizing function, for example standards conversion, compression and decompression, noise reduction, oversampling and filtering. Such additional functions will be referred to herein and in the claims as filtering, and will be understood to include such additional functions.
In the preferred embodiment of the invention it is taught to store and pass one or more secondary signal with the video signal in fashion which maintains proper time relationship between the video signal and the secondary signal.
The inventive concepts described herein are well suited for use in synchronizing satellite, microwave and telephone feeds, inter-suite connections and in house signals, thus eliminating the use of expensive and cumbersome multiple genlocking and timing schemes.
An improved video synchronizer as described in application Ser. No. 08/096,240 incorporated herein by reference.
A video synchronizer for multiple video signals of the same or different form for which the circuitry for each video signal may be separately constructed and which may be installed in various case configurations, with the common circuitry being shared by the multiple circuits.
A multiple electronic signal synchronizer configuration in which a single genlock circuit may be utilized to provide reference signals for multiple signal synchronizers, while retaining individual genlock phase controls for each output electronic signal.
A signal synchronizer in which one of the input signals is used as the reference.
A multiple electronic signal synchronizer which is configured to be used as an adjustable, fixed length delay, which use may be automatically switched.
A multiple signal synchronizer configured to use a selected one of the input signals as the reference to synchronize a plurality of input signals to one of the plurality, with the selection of the reference being automatically switched under known conditions.
A signal synchronizer capable of using recursive and nonrecursive adaptive filtering for noise reduction, image enhancement or other features.
A signal synchronizer capable of storing a full repetition period of the signal in memory. A video signal synchronizer capable of storing the entire video signal, including associated sync, timing, error checking and ancillary signals or portions so as to pass those signals or portions in addition to the active video portions.
A video synchronizer capable of selecting ones of the portions outside of the active video so that those portions may be preserved and passed or reconstructed and reinserted in the stored signals from the memory.
A video signal processing device having a memory for the video signal and having an additional memory capability for one or more related or unrelated secondary signals in order to achieve proper time relationship of the secondary signals with respect to the associated video signal.
These and other objects of the invention will become apparent to one skilled in the art from the description herein, taken in conjunction with the attached drawings.